Accommodative microfluctuations represent steady-state variability in the accommodative response.
43 Although their exact role in the accommodative response control is yet to be fully understood, current consensus is that microfluctuations serve as an “error” cue to quantify the magnitude and direction of the mean defocus level to help maintain appropriate accommodative responses.
30,43,44 Microfluctuations increase with increasing mean accommodative response. Results of the present study indicate that there were increased accommodative microfluctuations associated with refractive correction during the reading task, but the reverse finding was observed in the movie task. Moreover, in the reading task, increased variability in the accommodative response with refractive correction was associated with increased magnitude of accommodative response, although the observed association was weak. It is unclear why there was inter-task difference in the effect of correction on microfluctuations. Across the two tasks, when participants were tested without correction (see
Table 1), differences in microfluctuations were observed with increased microfluctuations in the movie task (t = −3.53,
P = 0.001). Data from the emmetropic participants (
n = 37), which were obtained during the process of finding hyperopic participants, showed similar trend in inter-task differences in microfluctuations (0.24 ± 10 D vs. 0.20 ± 0.10 D for movie and reading tasks, respectively, although it did not reach significance (t = −1.88,
P = 0.07). However, beyond any inherent inter-task differences in target characteristics, it would have been expected that with full correction of hyperopia, the extra accommodative demand due to uncorrected hyperopia would have been eliminated, thus reducing the activity of the accommodative plant (crystalline lens movement), resulting in a more stable accommodative response; which is consistent with the results obtained in the movie task. Nonetheless, the correlation between the RMSE of accommodative variability and the mean accommodative response during the reading task also suggests that perhaps with spectacle correction, microfluctuations of accommodation increased as a way of providing temporal directional sign for the accommodative controller to produce an appropriate response.
43 It is also possible that correction of hyperopia increases the sensitivity of the sensorimotor system (accommodative system) to maximize error detection, thus resulting in more fluctuations concurrent with increased accommodative response.
45